Bone Marrow-Derived Mesenchymal Stem Cells Enhance Angiocrine Gene Expression in Cultured Liver Sinusoidal Endothelial Cells

Background/Objectives: Liver sinusoidal endothelial cells (LSECs) support liver regeneration through angiocrine signaling, but they rapidly lose their specialized phenotype—including fenestrae and angiocrine gene expression—during chronic injury and in culture. Bone marrow-derived mesenchymal stem cells (BMSCs) act largely through paracrine mechanisms, yet their effects on the LSEC phenotype remain incompletely defined. Methods: Human and mouse LSECs were indirectly co-cultured with BMSCs, or with fibroblasts as an active stromal comparator, in a Transwell system for 24 and 72 h. Angiocrine gene expression was quantified by qPCR in three independent experiments per species (human: independent cultures from a single commercial cell lot; mouse: independently isolated LSEC preparations), the transcriptome of mouse LSECs was profiled by exploratory 3′ mRNA sequencing, and cell-surface ultrastructure was examined descriptively by scanning electron microscopy (SEM). Results: Relative to time-matched monocultures, BMSC co-culture increased VEGFA, WNT2 and WNT9B mRNA at both time points and NOS3 (eNOS) mRNA at 24 h in human LSECs, and Hgf and Vegfa (24 and 72 h) and Wnt9b (24 h) mRNA in mouse LSECs, whereas mouse Wnt2 was unchanged. These increases were larger than those observed with fibroblast co-culture, although fibroblasts also increased some of the same transcripts. In RNA sequencing (n = 2 per group, 24 h), 85 genes were differentially expressed (FDR < 0.05); Vegfa was increased together with a set of hypoxia-responsive and glycolytic transcripts, whereas Hgf, Wnt2 and Wnt9b were not significantly changed. Fenestrated, sieve-plate-like regions were present in selected SEM images of BMSC co-cultures; because the images were acquired selectively, they do not indicate whether fenestrae were more prevalent across the culture. Conclusions: Together, these in vitro findings show that BMSC-derived factors acting across a 0.4 μm Transwell membrane increase selected angiocrine transcripts in cultured LSEC preparations relative to time-matched monocultures. Whether this reflects preservation of the LSEC phenotype, and whether it alters angiocrine protein output or liver regeneration, remains to be determined.